From the upstream advisory [1]:
Under certain circumstances OpenSSL's internal certificate verification
routines can incorrectly accept a CRL whose nextUpdate field is in the past.
(CVE-2011-3207)
This issue applies to OpenSSL versions 1.0.0 through 1.0.0d. Versions of
OpenSSL before 1.0.0 are not affected.
Users of affected versions of OpenSSL should update to the OpenSSL 1.0.0e
release, which contains a patch to correct this issue.
Thanks to Kaspar Brand <ossl@velox.ch> for identifying this bug and
suggesting a fix.
Applications are only affected by the CRL checking vulnerability if they enable
OpenSSL's internal CRL checking which is off by default. For example by setting
the verification flag X509_V_FLAG_CRL_CHECK or X509_V_FLAG_CRL_CHECK_ALL.
Applications which use their own custom CRL checking (such as Apache) are not
affected.
[1] http://www.openssl.org/news/secadv_20110906.txt

This issue did not affect the versions of the openssl package, as shipped with
Red Hat Enterprise Linux 4 and 5.
This issue did not affect the version of the openssl096b package, as shipped
with Red Hat Enterprise Linux 4.
This issue did not affect the version of the openssl097a package, as shipped
with Red Hat Enterprise Linux 5.
This issue did not affect the version of the openssl098e package, as shipped
with Red Hat Enterprise Linux 6.